First Monday in December marks the day when shoppers get busy online, to have their purchases delivered in time for Christmas. Photograph Sarah Lee for the Guardian

Retailers are hoping that the Mega Monday online shopping spree marked the start of a Christmas rush after industry figures showed disappointing sales in November.

Predictions that as much as £450m would have gushed through online tills – making it Britain's busiest day on record for cyber-shopping – have brought comfort to retailers after last month saw sales growth drop to its slowest pace for seven months.

In a sign cash-strapped shoppers were putting off festive food buying and holding out for pre-Christmas discounts on gifts, the British Retail Consortium said November's sales were up just 0.6% on a year earlier once the effect of new store space was stripped out of the figures. It was the weakest performance since takings slumped amid a cold snap in April.

Demand for winter and party wear helped sell clothes and a more buoyant housing market saw homewares fare better, but food sales fell for the fourth month running according to the BRC's sales monitor, compiled with accountants KPMG.

There was "good demand" for festive desserts, party food and Christmas hampers and the "baking frenzy" continued, the report said. But consumer confidence weakened and, coupled with falling food prices, knocked sales for the category overall.

"It seems that once again, shoppers are leaving their festive food buying until later. Six in 10 tell us they will spend more time than last year hunting for the best deals, and four in 10 seeking the best quality," said Joanne Denney-Finch, chief executive of grocery researcher IGD, which provides the report's food data.

Overall, sales growth was ahead of where it was in the runup to Christmas 2012, when November sales rose just 0.4% on the year.

The BRC said this November saw a slow start and then growth "picked up in a big way" in the final week, when falling temperatures helped boost clothing sales.

Helen Dickinson, BRC director general, said: "Christmas spending looks on course to be an improvement on last year, but December will decide it."

Other reports suggested the make-or-break month for retailers had got off to a strong start.

Visa Europe estimated that £450m would have been spent online in 7.7m transactions by the close of business on Monday night, which would make this Mega Monday the busiest online shopping day recorded.

Mega Monday is one of many days retailers seek to highlight in the runup to Christmas. It marks the day when shoppers have just been paid for November and, having supposedly spent the weekend browsing, they then splash out online – allowing plenty of time for deliveries in time for Christmas. Retailers mark the day with offers and discounts, following hard on the heels of American import Black Friday – the day US retailers offer post-Thanksgiving discounts.

As ever more purchasing moves online the BRC said internet shopping again played a big role in boosting sales in November. Online sales of non-food products grew 16% on a year earlier, the strongest growth so far this year. One in every five pounds of non-food buying was done online last month, the highest proportion on record.

Overall, retailers should not bank on a bumper Christmas, economists warn. With inflation still outstripping wage growth and energy bills rising further this winter, many households will be short of money to splash out.